Insulation Testing during a condition report/periodic test.

Question

I understand why we connect line and neutral together and IR test them to earth. My question is, why not just test line to earth and neutral to earth? It&rsquo;s just that it&rsquo;s a bit fiddly connecting line to neutral sometimes. 
 Cheers

mapj1 · Accepted Answer

There may be loads connected L-N that mean that you will stress if you raise one side and not the other to 500VDC for the test. Traditional loads like filament lamps and DOL motors are unlikely to care, and in effect the insulation meter is seeing L and N in parallel anyway, but some modern electronics does not appreciate being held up in the air by one leg only.of course if you disconnecto all loads and fittings, then you can do separated L and N to gnd tests, but that really is a lot of work, compared to switching off at the incomer to remove the connection of the NE short at the substation, plugging in an L-N short and then testing from there to ground and in effect testing the whole site at once. 
 I agree if you have to break it down by sub circuit to find a problem it rapidly gets very tedious. Mike

Insulation Testing during a condition report/periodic test.

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